Problem: In math class, the girl to boy ratio is $4$ to $4$. If there are a total of $24$ students, how many girls are there?
A ratio of $4$ girls to $4$ boys means that a set of $8$ students will have $4$ girls and $4$ boys. A class of $24$ students has $3$ sets of $8$ students. Because we know that there are $4$ girls in each set of $8$ students, the class must have $3$ groups of $4$ girls each. There is a total of $12$ girls in math class.